Below are two example pairs of time-frequency and the corresponding GFP plots for the orange v. blue conditions. Data were calculated over the mean activity over 12 sensors.
I calculated the mean GFP by first obtaining the mean FT/cm within the dark greyed window time frame for each of the 12 sensors, then calculated the average (of the 12 sensors) of the averaged time windows. When running a t-test, no significant difference was found between the GFP activity for orange v. blue. I understand that the way the data were structured and the analysis pipeline for time-frequency analysis and GFP are different, so it might not be surprising that significance in one analysis might not translate to the other. However, in MEG papers that I have seen, it is common for GFP plot to show a much more prominent peak at the time window of interests that often corresponds with the time-frequency result.
My three questions here are,
1) Do GFP activity sometimes not capture significant activity seen in time-frequency analysis?
2) Would it be acceptable in peer review standards to have GFP activity not be consistent with the time-frequency output?
3) In my cases here, does it mean that there are low firing, but consistent sustained activity over time going in the alpha-beta range as opposed to the more typical event related single evoked activity spike?
Appreciate any advice here!